In an indoor environment, such as a large house or an office, a single access point (AP) often may not be able to cover the entire indoor area.
One straightforward attempt to solve this problem is to increase the transmission power. However, solely relying on increasing the transmission power on the AP would be a poor solution. In addition to regulatory bodies that limit the transmission power of the AP, it is typical that the wireless local area network (WLAN) communications link between an AP and a client is highly asymmetrical, that is, the client's transmission power is usually lower than the AP's transmission power. The client's antenna efficiency conventionally is also lower than the AP. Moreover, a portable client, e.g. a mobile phone, often is hand held by a user, and because of the signal absorption and disruption by the human body, signals from such portable client may reach the AP at even lower powers. Yet, many commonly used WLAN protocols require each side of the link to receive an acknowledgement (ACK) for the packets that are transmitted, e.g. in a downlink direction. If one side of the WLAN link cannot receive from the other side of the link, no packet can be transmitted to the other side of the link.
Instead of one AP with high transmission power and high performance antennas, an attractive alternative is using a multitude of smaller APs that are deployed in the environment in a scattered, distributed manner. These smaller APs form a wireless mesh network, and therefore are also called mesh points. When a client device establishes connection with one of the mesh points, the mesh points can forward the traffic to the mesh point that is connected to the gateway, which in turn communicates the traffic to the outside world, e.g. wide area network (WAN) and/or the Internet. However, there are also many challenges associated with implementing these wireless mesh networks, especially in a home environment where a layman user may be involved in installing and configuring these mesh points.
Generally speaking, as mentioned above, a better alternative to an access point (AP) with large transmission power is a wireless mesh network with a multitude of smaller APs, deployed in the environment in a scattered, distributed manner. These smaller APs (or mesh points) are often marketed as so-called “range extenders” or “repeaters.” A range extender generally works by associating itself to a user's main AP and receiving Internet connection from the main AP. Then, clients such as mobile phones, laptops, and desktop computers, and smart devices can associate to the range extender.
In many of these settings, it is up to the connection client to decide what happens, e.g. what action or reaction to take when a certain type of issues takes place, such as poor reception, in the wireless mesh network, which may adversely affect the efficiency and stability of such network. For example, roaming between the main AP and repeater can be a common issue where the clients may be stuck in a connection with the main AP or a repeater mesh point and may not roam to the mesh point that can provide the clients with the best throughput. All too often, roaming between multiple range extenders and the main AP may not function as designed, and different roaming methods may be required for different types of clients.
IEEE 802.11, commonly referred to as Wi-Fi, is widely used for wireless communications. Many deployed implementations have effective ranges of only a few hundred meters. To maintain communications, devices in motion that use it must handoff from one access point to another.
Handoffs are already supported under the preexisting standard. The fundamental architecture for handoffs is identical for 802.11 with and without 802.11r, i.e. the mobile device is entirely in charge of deciding when to hand off and to which access point it wishes to hand off.
The key negotiation protocol in 802.11i specifies that, for 802.1X-based authentication, the client is required to renegotiate its key with the RADIUS or other authentication server supporting Extensible Authentication Protocol (EAP) on every handoff. This is a time-consuming process.
The 802.11 Working Group standards k, r, and v let clients roam more seamlessly from AP to AP within the same network. IEEE 802.11k and 802.11r are industry standards that enable seamless Basic Service Set (BSS) transitions in the WLAN environment. The 802.11k standard provides information to discover the best available access point.
The 802.11k standard helps a device to speed up its search for nearby APs that are available as roaming targets by creating an optimized list of channels. When the signal strength of the current AP weakens, the device scans for target APs from this list.
802.11k is intended to improve the way traffic is distributed within a network. In a wireless LAN, each device normally connects to the AP that provides the strongest signal. Depending on the number and geographic locations of the subscribers, this arrangement can sometimes lead to excessive demand on one AP and under-utilization of others, resulting in degradation of overall network performance. In a network conforming to 802.11k, if the AP having the strongest signal is loaded to its full capacity, a wireless device is connected to one of the underutilized APs. Even though the signal may be weaker, the overall throughput is greater because more efficient use is made of the network resources.
In 802.11k, the following steps are performed before switching to a new access point: the access point determines that a client is moving away from it, the access point informs the client that it should prepare to switch to a new access point, the client requests a list of nearby access points, the access point provides a site report to the client, the client moves to best access point based on the report.
In 802.11k, therefore, roaming from AP to AP is client-centric.